1. Field of the Invention
The present invention relates to an air bag device including an air bag which is deployed into a vehicle compartment by a high-pressure gas generated by an inflater upon collision of a vehicle to hold back an occupant.
2. Description of the Related Art
In such air bag device, if the inflater for generating the high-pressure gas is disposed outside the air bag, a gas passage interconnecting the inflater and the air bag is required, resulting in an increase in the number of parts. Therefore, there is a conventionally known air bag device in which an inflater is disposed within an air bag to eliminate the need for the gas passage. In this case, a slit is defined in a base end of the air bag. The inflater is inserted through the slit into the air bag and fixed therein. Then the slit is closed, thereby preventing leakage of high-pressure gas from the air bag.
If the slit in the air bag is closed by sewing, there is a problem that the number of sewing steps is increased, causing an increase in cost. If the slit is closed in such a manner that it is covered with a special closing member, there is a problem that the number of parts is increased by the closing member and the number of assembling steps is also increased, likewise causing an increase in cost.
There is also an air bag device which is already known from Japanese Patent Application Laid-open No.10-129382, and in which a subassembly comprised of an air bag and an integrally formed inflater is accommodated in a case body of a module case, so that a lid covering the case body is opened upon collision of a vehicle, thereby permitting the air bag to be deployed into a vehicle compartment. The module case is closed by bringing hooks formed on the case body into engagement in hook-engaging bores defined in the lid. When the air bag is expanded within the case body, it pushes an inner surface of the lid whereby the engagement of the hooks in the hook-engaging bores is released to cause the lid to be opened.
In the above known air bag device, an outer peripheral surface of the lid protrudes outwards from an outer peripheral surface of the case body in the vicinity of an opened edge of the case body to form a stepped portion. Therefore, when an external force is applied to the stepped portion, there is a possibility that the engagement of the hooks in the hook-engaging bores will be released, causing the lid to be opened.
There is also an air bag device used upon a side collision of a vehicle, which is already proposed in Japanese Patent Application No.9-237960 and in which an air bag is formed by double-folding a substantially band-shaped base fabric, otherwise referred to herein as a xe2x80x9cground fabricxe2x80x9d, along a central folding line and sewing end edges of the round fabric excluding the folding line. Further, there is a process for folding an air bag in an air bag device used upon a side collision of a vehicle, which is already proposed in Japanese Patent Application No. 9-226787, and which comprises folding the air bag in a bellows-shaped fashion in a longitudinal direction from a tip end toward a base end, and then folding upper and lower portions of the folded air bag in the vertical direction. Yet further, there is an air bag device used upon a side collision of a vehicle, which is already known from Japanese Patent Application Laid-open No. 5-16751 and in which a tether for stabilizing the shape of the air bag upon the expansion of the air bag is sewn to a ground fabric in a state in which the tether has been superposed onto a reinforcing fabric, thereby reinforcing the sewn portion.
When the end edge of the ground fabric double-folded along the central folding line is sewn, as in the air bag device proposed in Japanese Patent Application No.9-237960, it is necessary to stop the sewing line at a location short of the folding line of the ground fabric to treat the end of a sewing thread. For this reason, there is a possibility that an unsewn portion may be created in the vicinity of the folding line of the ground fabric, whereby the undesirable leakage of a gas from the unsewn portion may be generated upon the expansion of the air bag.
When the air bag is folded in a bellows-shaped fashion from the tip end toward the base end, as in the air bag device proposed in Japanese Patent Application No.9-226787, the folding operation can be automated for most of the air bag, but cannot be automated for the base end of the air bag in which the inflater is accommodated. Therefore, it is required that the folding operation for the base end of the air bag must be conducted manually. When the operation of folding the air bag in the bellows-shaped fashion is conducted manually, there is a problem that it is difficult to conduct a precise folding operation free of a dispersion, if a mark as a criterion does not exist on the air bag. However, the provision of a special mark for the manually folding operation is undesirable, because it causes an increase in cost.
When the sewn area between the ground fabric and the tether is reinforced with the reinforcing fabric as in Japanese Patent Application Laid-open No.5-16751, the number of parts is increased by the reinforcing fabric, likewise resulting in a problem that it causes an increase in cost.
Accordingly, it is a first object of the present invention to ensure that the slit defined in the air bag in order to accommodate the inflater is closed reliably without use of a special closing member.
It is a second object of the present invention to prevent the lid, which covers the case body of the module case of the air bag device, from being opened inadvertently.
It is a third object of the present invention to ensure that the air bag is sewn, so that the performance upon the expansion of the air bag and the operability of folding the air bag can be ensured.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided an air bag device comprising an inflater which has a retainer retained thereon, and which is inserted into an air bag through a slit defined in a base end of the air bag, and a protector sheet wound around an outer periphery of the folded air bag, the slit in the air bag being closed by sandwiching the slit between the retainer and the protector sheet.
With the above arrangement, the slit defined in the base end of the air bag in order to insert the inflater having the retainer retained thereon into the air bag is closed by sandwiching it between the retainer and the protector sheet wound around the outer periphery of the folded air bag. Therefore, it is possible to prevent a high-pressure gas, generated by the inflater upon the expansion of the air bag, from being leaked through the slit without provision of a special member for closing the slit, whereby the air bag can be deployed reliably.
To achieve the second object, according to a second aspect and feature of the present invention, there is provided an air bag device comprising an air bag and an inflater for supplying a high-pressure gas to the air bag, the folded air bag and the inflater being accommodated in a module case comprising a case body which is openably and closably covered with a lid, a stepped portion formed in the vicinity of an opened edge of an outer periphery of the case body to stand back from an outer surface of the case body, a flange which is formed on an outer periphery of a lid and which is capable of being engaged with an outer periphery of the stepped portion, and a projection which is formed on a back of the lid and which is capable of being engaged with an inner surface of the opened edge of the case body, whereby the outer surface of the lid is positioned flush with the outer surface of the case body in a state in which the lid has been closed.
With the above arrangement, the stepped portion is formed in the vicinity of the opened edge of the outer periphery of the case body of the module case to stand back from the outer surface of the case body, and the flange capable of being engaged with the outer periphery of the stepped portion is formed on the outer periphery of the lid. Therefore, the case body and the lid are fitted with each other in socket-and-spigot type fitting, so that the outer surface of the lid is positioned flush with the outer surface of the case body. Thus, it is difficult for an external force to be applied to the flange of the lid, whereby the lid can be prevented from being opened inadvertently. Moreover, the projection capable of being engaged with the inner surface of the opened edge of the case body is formed on the back of the lid and therefore, the flange of the lid can be located reliably on the opened edge of the outer periphery of the case body to further reliably prevent the creation of a difference in level.
To achieve the third object, according to a third aspect and feature of the present invention, there is provided an air bag device comprising an air bag which is expanded by a high-pressure gas generated by an inflater upon collision of a vehicle to hold back an occupant, and which includes a sewing line extending along a double-overlapped end edge of a ground fabric double-folded along a central folding line, the air bag device including a patch fabric superposed onto the ground fabric to cover at least a portion in the vicinity of a tip end of the folding line, the sewing line extending on the patch fabric beyond the folding line.
With the above arrangement, when the ground fabric is sewn along the sewing line extending along the double-lapped end edge of the ground fabric double-folded along the central folding line, it is possible to prevent the sewing line from being ended at a location short of the folding line to leave an unsewn portion in the vicinity of the tip end of the folding line, thereby avoiding the leakage of the gas through the unsewn portion, because the sewing line extends on the patch fabric, superposed onto the ground fabric to cover a portion in the vicinity of the tip end of the folding line, beyond the folding line.
To achieve the third object, according to a fourth aspect and feature of the present invention, there is provided an air bag device comprising an air bag which is expanded by a high-pressure gas generated by an inflater upon collision of a vehicle to hold back an occupant, and which is made by superposing a reinforcing fabric onto a base end of a ground fabric and sewing the reinforcing fabric to the ground fabric along a sewing line, wherein the sewing line is disposed in parallel to a folding line along which the air bag is folded in a bellows-shaped fashion.
With the above arrangement, the sewing line, along which the reinforcing fabric is superposed and sewn onto the base end of the ground fabric, is disposed in parallel to the folding line along which the air bag is folded in the bellows-shaped fashion. Therefore, the air bag can be folded precisely using the sewing line as a mark. Moreover, it is unnecessary to provide a special mark and hence, an increase in the number of parts and an increase in cost can be avoided.
To achieve the third object, according to a fifth aspect and feature of the present invention, there is provided an air bag device comprising an air bag which is expanded by a high-pressure gas generated by an inflater upon collision of a vehicle to hold back an occupant, and which includes a tether for interconnecting opposed inner surfaces of a ground fabric to define the shape of the air bag upon the expansion of the air bag, wherein opposite ends of the tether are double-folded and sewn to the inner surface of the ground fabric.
With the above arrangement, the opposite ends of the tether interconnecting the opposed inner surfaces of the ground fabric to define the shape of the air bag upon the expansion of the air bag are double-folded and sewn to the inner surface of the ground fabric. Therefore, even if a strong tensile strength is applied to the opposite ends of the tether upon the expansion of the air bag, it is possible to reliably prevent the sewing line from being broken to break the ground fabric. Moreover, a special reinforcing fabric is not required and hence, an increase in the number of parts and an increase in cost can be avoided.